The following is what the Ethereum documentation of Oraclize says:
Firstly, in the most common case, a transaction executing a function of a smart contract is broadcasted by an user. The function contains a special instruction which manifest to Oraclize, who is constantly monitoring the Ethereum blockchain for such instruction, a request for data.
Secondly, according to the parameters of such request, Oraclize will fetch or compute a result, build, sign and broadcast the transaction carrying the result. In the default configuration, such transaction will execute the __callback function which should be placed in the smart contract by its developer: for this reason, this transaction is referred in the documentation as the Oraclize callback transaction.
What kind of instruction is executed? What messages are passed around when calling the oraclize_query
function?
Is the "special" instruction and oraclize_query
the same thing? As far as I understand, oraclize_query
is the request for data, right?
The other answers, don't address what the "special" instruction is, etc.